Operational Radiation Protection in Radiotherapy Flashcards
Name 2 radiation sources in radiotherapy and state the dose rate from that source.
- CT imaging - 0.3 mSv/s in bore centre
- SXT unit - 80 mSv/s at applicator
- Brachytherapy unit - 5000 mSv/s adjacent to source
- Linac unit - 250 mSv/s at beam portal
What are the risks to workers from therapeutic beams?
- Member of staff remains in the bunker during treatment.
- Maintenance staff work close to Klystron with HT on. (Klystron is radiation source)
- Radiographic staff regularly exposed to low level induced radioactivity in linac head.
- Maintenance staff work close to linac head following high energy exposure.
- For multiple source rooms, unintended exposure from ‘the other source’.
What are the risks to a MoP from therapeutic beams?
They may remain within the bunker during beam on without staff knowledge
What is in place to reduce the risks to staff & MoPs from therapeutic beams?
- CCTV in the bunker
- Interlocks
- Emergency stops
- Control of access
What does control of access do in terms of radiation protection?
- Ensures only patient is in the bunker
- Establishes who has authority over access (operator in charge)
What are common access rules?
Local rules common to many areas.
then have a set of local rules for that specific area
What binds a radiation worker to following local rules?
It is a condition of employment.
What does ‘handing over control’ of a room entail?
- SOPs will be different
- Local rules will change
- The responsible employer will change
- Equipment responsibility will change
What does an RT specific handover form contain?
- Formal removal from clinical service to prevent use prior to arrival of service engineer.
- Explicit statement on service agency LRs (have you seen their local rules)
- Requires statement of work (to enable local decision on appropriate QC)
What are the 3 types of safety controls in RT, and give 2 examples of each?
Engineering controls:
- Search buttons (incl button timing)
- Fail-safe door interlock
Procedural controls:
- Operator in control
- Last person out executes search button sequence
- Exposure initiator responsible for checking room empty
- Room monitoring (cameras, intercom)
Personal protective equipment:
- TLD badge
- Source handling tools
What is the purpose of each type of safety control in RT? (name and explain all 3)
Engineering – take away possibility of procedural error – design to fail safe = test this regularly.
Procedural – will one day go wrong as involves people remembering to do it
PPE – badge – prevents person from working with radiation if close to limit (future safety control – rather than immediate)
What is the purpose of beam on indicators and emergency stops?
Reduce the extent of accidental exposure if it happens.
Indicators and emergency stops in a number of places inside and outside the room that aim to move a person away from MV radiation (kV radiation buttons normally only on equipment itself).
What is the need for PPE based on?
Surveys taken from around the working beam. (environmental surveys as well as commissioning surveys).
What is the dose limit for non-radiation employees?
1 mSv (same as MoP)
What does IRR99 state about QA for RT?
Employer shall:
…make arrangements for a suitable quality assurance programme …for the purpose of ensuring that [the equipment] remains capable of restricting so far as is reasonably practicable exposure to the extent that this is compatible with the intended clinical purpose or research objective.
